Due to timing differences in the offer process and our decision-making phase, there were small changes to the floor plan, but I would argue that it cannot result in a difference of €150k.
The spread can even be larger.
Provider B spoke quite openly in the preliminary discussion about Provider A regarding
I would avoid such people; they like to leave you out in the cold when you need them.
I want to build a solid house and accordingly want a solid basis with good quality in both materials and workmanship. But €150k?
What you posted from both construction service descriptions is incomplete and therefore not comparable. You would need to know the exact wording, but you can hardly expect that from laypeople here.
From experience, I would guess that you have chosen two providers who could not be more extreme. Even if the design deviates from the usual—less so because it disguises a recessed top floor, but because of the many recesses—the price probably lies in the middle. I would discard both and not consider them further.
There are many providers in MV as well; go to new development areas and talk to homeowners there, ask them about their experiences, or find a supervising architect. But make sure to ask for references.